Transient load compensating system for hydraulic governors



Nov. 3, 1959 A. G. MASSEY TRANSIENT LOAD COMPENSATING SYSTEM FOR HYDRAULIC GOVERNORS Filed April l8. 1956 INVENTOR. ALBER r 67 MA55Y BY rmylw-w ATTORNEY TRANSIENT LOAD COMPENSATING SYSTEM FOR HYDRAULIC GOVERNORS Albert G. Massey, Watertown, N.Y., assignor to Curtiss- Wright Corporation, New York, N.Y., a corporation of Delaware Application April 18, 1956, Serial No. 579,072

4 Claims. (Cl. 121-42) The invention relates to engine speed control mechanisms and particularly to engine governors operating as hydraulic amplifiers (commonly called hydraulic relay or simply hydraulic governors). An example of such a governor mechanism is shown diagrammatically in the single view on the accompanying drawing, the mechanism including anti-hunting feedback or compensating means operating hydraulically and of the type shown in United States patent to A. H. Rodeck and myself 2,715,891 issued August 23, 1955, entitled Hydraulic Governor Compensating System.

While hydraulic governors for engines can be made extremely sensitive to small changes in engine speed and can be designed to control engine fuel input in a manner to obtain close speed regulation these mechanisms as usually arranged cannot be made to eflect timely or sufliciently rapid correction for sudden or highly temporary load changes and particularly transient electrical load changes in engine-generator systems. The reason is that an electrical load change must be of substantial duration in order to result in deviation of engine speed from reference value. An object of the present invention is to provide in a governor for engines an improved load-signal-responsive mechanism capable. of action in anticipation of engine speed changes.

Another object is to provide an improved transient load compensating system for use in connection with a hydraulic speed control governor or in combination therewith, the system being operable in part through the agency of the power output hydraulic mechanism of the governor but in such manner as never to interfere with the normal functioning of the governor to make proper corrections in response to speed deviations detected by it.

Another object is to provide an electrical load change sensing temporary modifier for the output or servomotor action of a hydraulic governor wherein the duration of time through which modification of governor output action takes place can be easily and effectually adjusted, a further object being to provide such an arrangement as just above outlined wherein the rate of movement of the governor output motor mechanism can be limited for transient load compensation action without interfering with rates of movement appropriate for speed correction generally. Other objects will be made apparent in the following description.

Referring to the governor mechanism as shown in the accompanying drawing, -a power case or main portion of the governor housing is indicated at 1, a speed sensing or error detecting mechanism is generally designated S (comprising as shown flyweights 3 connected to operate a pilot valve plunger 4 and a counterpoisespring 5 opposing flyweight action on the plunger and .capable of suitable adjustment for speed setting). Mechanism S is driven by a shaft 6 as a function of engine speed, and, since the principal illustrated portion ofshaft 6 is tubular and otherwise adapted to serve as a valve sleeve I S in the proper directions incident to fuel-on and fueltem generally similar to that of Patent 2,715,891.

Patented Nov. 3, 1959 housing 1. The piston 7 is shown connected by linkage elements 9. and 10 to a terminal or governor output shaft 12 for connection with the fuel metering means of an engine.

For control of motor mechanism M, the pilot valve plunger 4, when moved upwardly or downwardly from its illustrated neutral position in which lands 17 and 19 close conduits 16 and 18 connected to motor cylinder chambers 8a and 8b respectively, diverts pressure fluid from a source such as partially represented by conduit 14 to one of said chambers 8a or 8b, meanwhile spilling fluid from the other chamber to the governor sump 25 through one or the other of conduits 22 and 24. For example, downward movement of valve plunger 4, in response to a detected drop in engine speed, connects the valve chamber 20 of valve sleeve 6 with motor chamber 8b via conduit 18 to initiate fuel-on motor movement, fluid being spilled from chamber 8a via conduits 16 and 22. Upward movement of the pilot valve plunger has the opposite effect and initiates fuel-off motor movement. Oil level in the governor case, as at L, is such that the various valving elements and connected passages, to be further described below, are continuously submerged.

Coordination of engine response to fuel adjustment with governor action, for stable governing, is accomplished by action of a hydraulic fluid compensation sys- The system herein shown comprises an actuatorpump piston 30 in a cylinder or chamber 31, the piston being connected, as through a link 30a for operation as a function of fuel metering output of the governor. Chamber 31 is connected through a generally closed conduit 32 to a compensation fluid receiving chamber 33 formed in part by a lower end portion of the bore of valve sleeve 6 below the pilot valve plunger 4. Pressure change in the chamber 31 and conduit 32 as a function of engine fuel metering operation is yieldably transmitted to the governor pilot valve plunger 4, thus in effect temporarily modifying the speed setting of speeder spring 5 versus flyweight force. As shown, a proportioner piston 34, freely slidable in the bore of valve sleeve 6, forms a movable wall of compensation fluid receiving chamber' 4; Spring 36 bears axially at its opposite ends on piston 34 and a seat member 33 in the bottom of compensation fluid chamber 33. Member 33 has a portion loosely entering the spring 36 to hold the spring approximately coaxial with the bore of the valve sleeve 6. Such arrangement of a pair of mutually opposed springs 35 and 36 and proportioner piston 34 enables initial approximately unrestrained axial movement of the pilot .valve plunger 4 in response to detected speed change by speed sensing mechanism S and, during speed correction operations of the governor, biases the forces produced by or acting upon the various elements said mechanism off? movements of the governor terminal. shaft. The biasing action on mechanism S is temporary through provision of a leak orifice 33 which restores the pressure inthe compensation system to that ofv sumpj 25. The orifice 38- is adjustable as by means of a needle-l-valve; 39- to enable coordination of the described compensation action in point of time with response of: the engineto fuel adjustments.

The proportioner piston and spring mechanism 34*36 is readily removable through the top of the bore of thepilot. valve sleeve 6 (e.g. for changing one or both of the springs 35- and 36, hence their modifying. action as a result of a fixed amount of compensation fluid: system pressure change), and, if. desired,- the working: parts of thev proportioner mechanism (piston and both springs) can be interconnected and secured to the lower end of the' pilot valve plunger 4 for removal from the valve sleeve 6 with the plunger. Further, if the spring 35 is connected for push-and-pull biasing action'of the proportioner piston 34 on and through the pilot valve plunger, then the spring 36 can be omitted from the construction without requiring any further change in it.

The transient load compensating mechanism hereof includes a transient-load-responsive valve plunger 40, slidable in a'bore of housing 1 for'example and subjected'to a load function other than engine speed. The vailving. arrangement, as shown, is operatingly in parallel relationship to the main governor pilot valve and? power piston mechanism, via portions of the already described fluid passages (cg. 14, l6, 18 etc.) as will'be apparent.

As illustrated, a chamber portion 42 of valve bore 41,. defined in part by axially spaced apart lands 47 and-49 of the plunger so, is supplied with governor oil under pressure through a portion 14' of passage 14. Thelands 4'7 and 49 normally close branch ports or passages 44 and drespectively of the power piston cylinder supply and spill passages 16 and 18. The valve plunger 44), in its illustrated neutral position, is subjectedto zero axial net forces since governor oil pressure in chamber 42 acts equally and oppositely on the two landportions' 47 and 4? of the valve plunger. Thus during'gove'rnor operation the plunger is self centering in the neutral position. The plunger 49 is also supported in its neutral position by a suitable coil spring located in the lower dead end of bore 41. The spring 4 5 is normally under no strain (other than that required to support the weight of the plunger). In order that the valve plunger 40, prior to commencement of governor operation, will be certain to occupy its neutral position the axial position of the plunger can be adjusted by a movable seat 45 for the spring. Upwardly beyond the land 47 of the valve plunger 40 and in spaced relation to land 47 the plunger 40 has a piston portion Sit slidable in bore 41. The necked portion 52 or" the plunger between: land 47 and piston portion 50 is disposed in a chamberportion 51 of bore 41 which is always connected to governor sump, as through a portion 22 of spill passage 22.

It will be apparent from inspection of the drawing:

that a predetermined downward movement ofthe transient-load-responsive valve plunger 40 results in fuelon actuation of power piston 7 which is-the same-result as accomplished by downward movement of the governor pilot-valve plunger 4. However, the operations of the signals indicative of transient load.(e.g. variations: in

electrical loading of a generator connected :to. the gov-- and engine) an electrornagnetically operated actuator:

mechanism, generally indicated at E, is shown as arranged to act on the plunger 49 in opposite directions.

through a hydraulic column 60 of variable length. Armature 54 and associated signal-receiving and armatureactuating or solenoid coil 55 are mounted in a casing, not shown, in alignment with the bore 41 of valve plunger 40. Variations of current in the coil 55, through connection of the coil with the generator output in a suitable manner as known in the electrical art, varies the axial position of the armature 54 as a function of generator output; A- spring: shown as interposed. between the governor housingan'd a shoulder 66 of the armature 54 normally holds the armature in an off center position relative to the coil 55. A stem portion 56 of the armature 54, as shown, extends loosely into the top of bore 41 and carries a piston 58 slidably mating said bore. The hydraulic column 60 disposed between the piston portion 59 of the valve plunger 40 and the electromagnetically actuated piston 58 is connected, as through a passage 61, to a continuously submerged portion of'the governor sump. A timing restriction 62 in the passage 61 is adjustably variable as by a needle valve 64. The leakprovided by the adjustable orifice 62 normally maintains the column of fluid 69 at negligible {c.g. atmospheric) pressure.

When current supplied to the coil 55 is at a predetermined value assumed to correspond to the governed speed of the engine, the armature 54 is maintained by the opposing magnetic and spring forces steadily in apredetermined oil center position in respect to the coil. It willbe apparent that a transient increase in current in the coil 55 results in downward movement of the armature 54 and its piston 58 against the opposing force of spring 65 so that the fluid pressure in chamber 60 is increased, thereby lowering the valve plunger 45} a distance approximately proportional to the amount of armature movement. This causes a substantially immediate enginefuel-increasing movement of the governor terminal shaft 12. The transient-load-compensating action is temporary, as determined by the adiustment of the needle valve 64, and'the valve plunger it? is returned by the centering action of pressure fluid in the chamber 42 on the land portions 47" and 49 into its illustrated neutral position to close both fluid passages 44- and 46 leading to the power piston cylinder.

Decrease incurrent from reference value in the solenoid coil 55 has the opposite effect of the operation just described above, the spring 65 in such case causing lowering of pressure in column 69, lifting of the valve plunger 40- and resulting in an appropriately temporaryfuel-decreasing governor output movement.

While, in the absence of suitable speed responsive governor mechanism, the fuel metering adjustment accomplished by the above described temporary action of the transient load compensating system hereof would tend to cause a permanent deviation in engine speed from reference' value, the normal or previously described action of the governor speed sensing mechanism 2 on the governor. pilot valve 4, immediately following the transient load change, prevents any permanent deviation of speed from taking place.

Since the rate of movement of the governor power piston 7 during the transient load compensating action of the present system increases with the amount o f opening of the ports controlled by the valve plunger 40, it

is desirable to limit the rateof piston movement inorder to prevent 'overcorrection in event of large transient load deviations. Such limiting, or damping of excessive movement, can be accomplished by adjustably restricting the passages 44 and 46 by suitable valves 68 and 70in the branch passages-44 and 46. Since, in.

the illustrated (double acting) power piston mechanism, the branch. passages 44 and 46 serve for motorfluid admission and spill, one valve in one of those passages or,..

alternatively, a suitable adjustable valve, not shown, in

the supply passage portion 14' leading to chamber 42) can be used for damping or piston stroke limiting.

In adapting the present transient load compensating system to hydraulic governors having types of output motor action different from the one illustrated herewith the transient-load-responsive valve (plunger 40 andythe rest) would, of course, be modified accordingly.

I claim: I I I 1. In combination with a hydraulic governor for controlling the speed of an engine, the governor including a hydraulic governor output motor; engine-speed-responsive means including a pilot valve mechanism operative to control pressure fluid for operation of the motor, a separate valve means connected to said motor and capable of initiating operation of the motor independently of enginespeed-responsive movements of the pilot valve mechanism, motor means adapted to be rendered automatically operative in response to signals other than such as are indicative of change in engine speed, said motor means being connected to said separate valve means for initiating its operation to actuate the governor output motor, and a device including a hydraulic column between said signal- -responsive motor means and said separate valve means,

and adjustable orifice means connected with the column and operative to limit the duration of time the separate valve means can control pressure fluid for producing movement of the governor output motor.

2. In a hydraulic relay governor for engines carrying electrical loads, said governor having a governor output hydraulic motor, a speed responsive pilot valve mechanism arranged to control fluid for operation of the motor, and a hydraulic compensation system between the motor and pilot valve mechanism operative to enable control of the engine at a set or reference speed under varying engine load, a second valve mechanism hydraulically in parallel with the pilot valve mechanism and governor output motor and independently of the compensation system so as to be capable ofefiecting movements of the output motor independently of operation of the pilot valve mechanism, means tending to maintain the second valve mechanism in a neutral position in respect to eflecting governor outputfmotor movement or operation, motor means adapted to be responsive to an electrical load signal, and means for transmitting operation thereof temporarily to the second valve mechanism at occurrence of each load signal, whereby transient electrical load deviations can effect movements of the governor output motor in directions tending to correct speed in advance of occurrence of engine speed change and without interference with speed-responsive action of the pilot valve mechanism, and whereby the compensation system can operate independently of. the second valve mechanism, or following its operation, to prevent the occurrence of permanent deviations ofengine speed from a set or reference value. e

3. In combination with a hydraulic governor for controlling the speed of an engine connected to drive an electrical generator, the governor comprising a fluid pressure source, speed responsive means, a hydraulic governor output motor and a pilot valve mechanism connected for operation by the speed-responsive means and operative tocontrol pressure fluid of said source for initiating operations of the motor in two directions, a separate valve I mechanism arranged to control fluid of said source in a speed-responsive pilot valve mechanism arranged to control pressure fluid for efiecting movement of a governor output hydraulic motor; a separate valve means operatingly in parallel with the pilot valve mechanism in respect to the hydraulic motor so as to be capable of initiating governor output motor movement independently of operation of the pilot valve mechanism, a motor device adapted for operation as a function of a signal other than engine speed, means normally maintaining said separate valve means in a neutral condition such as then to be incapable of initiating governor output motor movement, motion transmitting hydraulic means between said motor device and said separate valve means, the hydraulic means defining a generally closed chamber for hydraulic fluid normally under negligible pressure, wall portions of the chamber including actuating displacement means connected to an output element of the motor device and actuated displacement means connected to operate the separate valve means, and an adjustable orifice communicating with the chamber to restore the pressure of fluid therein to negligible value a desired or predetermined time after each operation of the motor device.

. References Cited in'the file of this patent UNITED STATES PATENTS 1,231,628 Lehr July 3, 1917 2,014,365 Beckett Sept. 17, 1935 2,391,629 Keller Dec. 25, 1945 2,423,191 Kopp July 1, 1947 2,503,362 Sweet Apr. 11, 1950 2,766,731 Brandes Oct. 16, 1956 2,812,746 Reggio Nov. 12, 1957 

